Explaining the Lyman-alpha forest
Abstract
Description
It is shown that many properties of Ly-alpha forest absorbers can be derived using simple physical arguments. Analytical expressions are derived for the density and the size of an absorber as a function of its neutral hydrogen column density, which agree well with both observations and hydrodynamical simulations. An expression is presented to compute Omega_IGM from the observed column density distribution, independent of the overall shape of the absorbers. Application to the observed column density distribution shows that at high redshift most of the baryons are in the forest and suggests a simple interpretation for its shape and evolution.
4 pages, 2 figures, to appear in the proceedings of the XVIIth IAP Colloquium, Paris, June 2001
4 pages, 2 figures, to appear in the proceedings of the XVIIth IAP Colloquium, Paris, June 2001